The present invention relates to an image processing method and apparatus and, more particularly, to an image processing method and apparatus for enlarging/reducing image data and converting resolution.
Conventionally, in digital image processing systems, an image has been recorded on a recording medium in the form of a dot pattern.
Further, conventional image processing devices such as a printer, a copying machine and a facsimile machine have recorded a dot pattern image as an output image on recording material such as paper and a thin plastic film.
Such image processing devices are divided into ink-jet printing type devices, wire-dot printing type devices, thermal printing type devices, laser-beam printing type devices and the like, depending upon printing method. The ink-jet printing type printer discharges ink droplets from the discharging orifices of a printing head and fixes the discharged ink on to a recording material.
Recent popularization of such image processing devices has raised needs for high-speed recording, high resolution, high image quality, lower noise and so on. Further, color ink-jet printing has been quickly developed.
Moreover, as high-level functions of the image processing devices have been developed, techniques such as image enlargement/reduction processing and resolution conversion have been greatly improved.
However, the above conventional devices have the following drawbacks:
(1) As high-level image-processing functions are developed, algorithms for such processings become complicated. As a result, processing speeds are lowered to a great extent. Conversely, in a case where image processing performance is suppressed for the purpose of maintaining a high processing speed, problems regarding image quality, e.g., lack of thin lines within an image or change of color hue upon image enlargement/reduction due to a change of color-representing pattern have occurred. PA1 (2) Upon resolution conversion, more serious problems have occurred. For example, regular thinning, such as the technique of thinning one dot from a predetermined number of dots, has changed the overall color hue of an image, and further generated a texture of different color hue.
Since no general solution to these problems have been provided, users have to adjust various processing parameters in accordance with the particular image to be processed.
Such adjustment greatly depends upon the user's ability, and therefore, the users require must be skilled in the adjusting technique.